Iraq has revised higher the death toll of citizens killed by U.S. private security guards from Blackwater USA in a shooting incident in Baghdad last month.

An Iraqi government spokesman, Ali al-Dabbagh, said the government's official investigation found that the death toll in the September 16 shootings was 17, six more than the 11 deaths previously reported.

Iraqi investigators said the shootings were a deliberate crime. Dabbagh said the probe revealed that the U.S. diplomatic convoy the guards were protecting did not come under direct or indirect fire.

Dabbagh said Iraq could take legal steps against the security guards for the deaths, and the government could also hold the security firm accountable.

Iraqi Prime Minister Nouri al-Maliki had ordered the investigation. The U.S. military and the FBI are also probing the fatal incident.

Last week, U.S. Secretary of State Condoleezza Rice ordered that U.S. government agents must accompany controversial private security guards working in Iraq.

Blackwater USA is the largest of three private security firms protecting U.S. diplomats in Iraq. The enhanced oversight will initially apply only to Blackwater guards.

The head of Blackwater USA, Erik Prince, has defended his employees' actions, saying they were purely defensive.